The purpose of this core remains the centralization of repetitive preparations of several items that are "starting materials" and are used by one or more of the projects. We have found this approach to be efficient and convenient for all concerned. It allows the core technicians to master a small number of difficult tasks; when one is temporarily absent or needs to be replaced the work does not stop; and there is a continuous supply of high quality material available to the users. The common core facility, equipment, and routine supplies, administered and supervised by a research scientist with appropriate expertise, is also quite economical. The preparations to be made by the core are: 1. Primary cultures of neonatal rat cardiac myocytes, and adult rat cardiac myocytes either in suspension or as plated cultures, to be used by Projects 1, 11, and some of the experiments of Project 12 that will be done in Toledo. 2. Preparations of crude Sf-21 insect cell membranes containing the recombinant H+/K+-ATPase to be used by Project 10. 3. Preparation of purified recombinant Src expressed in Sf-9 cells, to be used primarily by Project 10. 4. Preparations of cardiac sarcolemmal membranes from beef and rat heart ventricles, to be used primarily by Project 1. 5. Preparation of purified Na+/K+-ATPase from pig kidney, to be used primarily by Project 11, and to smaller extents by Projects 1 and 10.